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March 17, 2011 -- Decade-old heart attack scars healed after being injected with stem cells from a patients' own bone marrow.

So far, eight patients have received the experimental treatment in an ongoing clinical trial. All eight had suffered heart attacks an average of 5 1/2 years prior; one of the patients had his heart attack 11 years earlier.

"These are chronic heart failure patients ... with really bad [heart attack damage] and big [heart attack] scars," study leader Joshua Hare, MD, tells WebMD. "We wanted to see if the cells would heal the scarred area and allow it to start working again."

They do, at least according to early results from a study under way at the University of Miami Miller School of Medicine.

Hare's team enrolled eight men at an average age of 57 who had heart attacks four months to 11 years earlier. All had dangerously enlarged hearts, with areas of scar tissue from their heart attacks.

The researchers harvested bone marrow progenitor cells from four patients and adult stem cells from another four patients. Using a catheter, they then injected the cells into the walls of the patients' hearts.

Within three months, the scarred areas of the patients' hearts began to work again. About six months after treatment, and for a year later -- the length of the study so far -- all eight hearts regained a more normal size. They shrank 15% to 20%, three times more than current treatments can achieve.

"If these bone marrow-derived cells did not have the capacity for regeneration, you would not expect them to make a dead scar start to function again," Hare says. "That is really the big deal here. We took two types of cells, whether just plain old bone marrow or [adult stem] cells, injected them right into the scar, and we were amazed. Three months later, the area that was completely dead started to contract again."

Heart stem cell expert Arshed Quyyumi, MD, professor of medicine and cardiology at Atlanta's Emory University, notes that stem cells are being explored in the treatment of people with recent heart attack damage -- but the "landmark area" of the Hare study is the use of stem cells to treat end-stage heart failure.

"The excitement here is that for these dangerously enlarged hearts, in spite of the [heart attack damage] being old, there is something that actually reverses the enlargement and their propensity to get worse," Quyyumi tells WebMD.

Quyyumi, who was not involved in the Hare study, notes that much more work must be done to confirm the findings, to find out exactly which bone marrow cells can heal hearts, and to find out how many of these cells are needed.

The Hare study continues to enroll patients, and a larger clinical trial is under way. Hare hopes that further studies will confirm his early results. If so, the treatment could be available to patients well before the end of the decade.

"This is on the horizon for people who need it," Hare says.

The Hare study appears in the March 17 online edition of the journal Circulation Research.